检查 Javascript 中的正整数：性能和安全性
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Check for positive integers in Javascript: performance and security
提问by Lucky Soni
I have written (and copied) a few lines of Javascript and it serves my purpose well. But I am trying to figure out a better way (cross-browser and better performance) of doing this. I copied the isIntegerfunction from a friend but I do not understand why we are checking against a string value in the following condition:
我已经编写（并复制）了几行 Javascript，它很好地满足了我的目的。但我正试图找出一种更好的方法（跨浏览器和更好的性能）来做到这一点。我isInteger从朋友那里复制了该函数，但我不明白为什么我们要在以下条件下检查字符串值：
if (((c < "0") || (c > "9"))) return false;
The above condition works fine but when I change it to check against number values, the functionality breaks. The input field starts accepting alphabetical characters. Here is how it looks when I change it:
上述条件工作正常，但是当我更改它以检查数字值时，功能会中断。输入字段开始接受字母字符。这是我更改它时的外观：
if ((( c < 0 ) || ( c > 9 ) return false;
I have tried to comment out sections so that you can understand what's happening. Also are there any security holes in this code? I read that the 1innerHTML1 method can open some security holes and hence we need to perform a 'clean' operation with it. Hence I chose to use jQuery's .htmlmethod (I am new to JavaScript)
我试图注释掉部分，以便您了解正在发生的事情。这段代码中还有安全漏洞吗？我读到 1innerHTML1 方法可以打开一些安全漏洞，因此我们需要对它执行“干净”操作。因此我选择使用 jQuery 的.html方法（我是 JavaScript 新手）
The page in question: http://thehotdeal.net/clients/wehtmlit/index.php?order/
有问题的页面：http: //thehotdeal.net/clients/wehtmlit/index.php?order/
$(document).ready(function() {
var total = 0;
function calcTotal() {
/* fetching some values from PHP variables and then performing calculations.
essentially this is multiplying number of pages by price per page
*/
/* <![CDATA[ */
var total_price_main_pages = ($("#pages").attr("value")) * (<?php echo $main_price; ?>),
total_price_sub_pages = ($("#subpages").attr("value")) * (<?php echo $sub_price; ?>);
/* ]] > */
$("input.calculate:checked").each(function() {
// This happens for each checked input field
// These are few additional otions available to the user. If selected then
// the price stored in their "data" attribute is added to the total
var value = $(this).attr("data");
total += parseInt(value);
});
total += (parseInt(total_price_main_pages)) + (parseInt(total_price_sub_pages));
$("#total").html("Total: <strong>" + total + "</strong>");
}
// This happens when the page loads
calcTotal();
$("input.calculate").click(function() {
total = 0;
calcTotal();
});
// function to check if an input is positive number(s). returns true if [ 0 <= s <= 9 ]
function isInteger(s) {
var i;
for (i = 0; i < s.length; i++) {
var c = s.charAt(i);
if (((c < "0") || (c > "9"))) return false;
}
return true;
}
// Checking the mainpage input (default value 1)
// (valid value is greater than or equal to 1 and less than 10)
$("#pages").keyup(function() {
var page = $(this).val();
// if user deletes the value in this input (blank)
// then just display a warning message and do nothing
if(page == ""){
this.value = "";
$("#pageError").html("Please enter a value equal or greater than 1.");
return false;
}
// if value is less than or equal to zero then
// then set 1 as the new value, remove the error message and call the calcTotal function
else if(page <= 0){
this.value =1;
$("#pageError").empty();
total = 0;
calcTotal();
}
// check if value is not a positive integer by calling the isInteger function
// if not a positive integer then set 1 as the new value,
//remove the error message and call the calcTotal function
else if(!isInteger(page)){
this.value =1;
$("#pageError").empty();
total = 0;
calcTotal();
}
// if value does not fall in any of the if statements i.e. value is acceptable
// remove the error message and call the calcTotal function
$("#pageError").empty();
total = 0;
calcTotal();
});
// check if value is not empty when user exits the input
// if empty then set value as 1, remove error message and call calcTotal function
$("#pages").blur(function() {
var page = $(this).val();
if(page == ""){
this.value = 1;
$("#pageError").empty();
total = 0;
calcTotal();
}
});
// Checking the subpage input (default value 0)
// (valid value is greater than or equal to 0 but less than 10)
$("#subpages").keyup(function() {
var page = $(this).val();
if(page == ""){
this.value = "";
return false;
} else if(!isInteger(page)){
this.value = 0;
total = 0;
calcTotal();
}
total = 0;
calcTotal();
});
$("#subpages").blur(function() {
var page = $(this).val();
if(page == ""){
this.value = 0;
total = 0;
calcTotal();
}
});
});
回答by Matt Ball
i do not understand why we are checking against a string value in the following condition
我不明白为什么我们要在以下条件下检查字符串值
Because cis a character (really, a 1-character string), since that's what String.charAtreturns. That said, the isIntegerfunction could be written much more simply using a regex:
因为c是一个字符（实际上是一个 1 个字符的字符串），因为这就是String.charAt返回的内容。也就是说，isInteger可以使用正则表达式更简单地编写函数：
function isPositiveInteger(s)
{
return !!s.match(/^[0-9]+$/);
// or Rob W suggests
return /^\d+$/.test(s);
}
or you could take another approach: convert the string to a number, make sure it's positive, and make sure that the floor of the number is the same as the original (thus it's an integer):
或者您可以采取另一种方法：将字符串转换为数字，确保它是正数，并确保数字的下限与原始数字相同（因此它是一个整数）：
function isPositiveInteger(s)
{
var i = +s; // convert to a number
if (i < 0) return false; // make sure it's positive
if (i != ~~i) return false; // make sure there's no decimal part
return true;
}
回答by jAndy
What about..
关于什么..
if( +inputString > 0 ) {
}
if its just about finding out if the input is a positive integer. If you also don't want to allow numbers with decimal points / floating point values, you should do with with input field validation like
如果它只是找出输入是否为正整数。如果您也不想允许带有小数点/浮点值的数字，则应该使用输入字段验证，例如
<input type="text" pattern="\d+" required/>
This tells the inputfield to only only numbers. The requiredflag is optional, if present it won't allow any submitbutton to continue unless all patternsare satisfied.
这告诉输入字段只有数字。该required标志是可选的，如果存在，它将不允许任何提交按钮继续，除非满足所有模式。
